Hormonal and genetic factors interact to influence mammalian brain sexual differentiation. Imbalances or defects in these factors often lead to abnormalities in sexual development. Syndromes of androgen non-responsiveness occur in many mammals, including humans and mice (Tfm), causing affected X/Y animals to be incompletely masculinized and partially feminized and are accordingly termed testicular feminization. We have shown that the hypothalamus/preoptic area and cerebellum of the Tfm mouse are deficient in androgen-binding macromolecules, as are other tissues, and have used this mutant as a genetic control to establish the existence and preliminary characteristics of this putative androgen receptor in normal mouse brain. While continuing to use this mouse mutant as a control to study the interactions of this macromolecule with steroid hormones and with intracellular components, we will further characterize the mutation itself. We also will examine several other strains of mice, including Recombinant-Inbred (RI) strains of mice which allow rapid genetic analyses, to reveal the numbers and kinds of genetic determinants responsible for the components of sex steroid reception in developing mouse brain. Having shown reciprocal interaction of androgens and estrogens with the respective estrogen- and androgen-binding macromolecules, we will use DNA-cellulose affinity chromatography, which separates these proteins, to further characterize these putative receptors and test our earlier hypothesis that they function as a reception mechanism that directly detects ratios of circulating androgens and estrogens. With DNA-cellulose chromatography, and with a selective serum factor we have discovered, we will resolve whether the estradiol receptors in hypothalamus and uterus have different properties, as suggested by our earlier studies. To evaluate the roles of the sex steroids and their specific binding proteins at the cellular level, we will complement the biochemical studies with autoradiography to detect cellular accumulation of injected 3H-steroids and with tissue cultures of dispersed hypothalamic cells to allow study of cellular responses to steroids. All of these studies will be interconnected by comparative genetic analyses of inbred mutant strains, the rationale for uniquely choosing the mouse for probing these questions.